- pvlib.spectrum.calc_spectral_mismatch_field(sr, e_sun, e_ref=None)#
Calculate spectral mismatch between a test device and broadband reference device under specified solar spectral irradiance conditions.
sr (pandas.Series) – The relative spectral response of one (photovoltaic) test device. The index of the Series must contain wavelength values in nm. [-]
e_sun (pandas.DataFrame or pandas.Series) – One or more measured solar irradiance spectra in a pandas.DataFrame having wavelength in nm as column index. A single spectrum may be be given as a pandas.Series having wavelength in nm as index. [(W/m^2)/nm]
e_ref (pandas.Series, optional) – The reference spectrum to use for the mismatch calculation. The index of the Series must contain wavelength values in nm. The default is the ASTM G173-03 global tilted spectrum. [(W/m^2)/nm]
smm (pandas.Series or float if a single measured spectrum is provided. [-])
Measured solar spectral irradiance usually covers a wavelength range that is smaller than the range considered as broadband irradiance. The infrared limit for the former typically lies around 1100 or 1600 nm, whereas the latter extends to around 2800 or 4000 nm. To avoid imbalance between the magnitudes of the integrated spectra (the broadband values) this function truncates the reference spectrum to the same range as the measured (or simulated) field spectra. The assumption implicit in this truncation is that the energy in the unmeasured wavelength range is the same fraction of the broadband energy for both the measured spectra and the reference spectrum.
If the default reference spectrum is used it is linearly interpolated to the wavelengths of the measured spectrum, but if a reference spectrum is provided via the parameter
e_refit is used without change. This makes it possible to avoid interpolation, or to use a different method of interpolation, or to avoid truncation.
The spectral response is linearly interpolated to the wavelengths of each spectrum with which is it multiplied internally (
e_ref). If the wavelengths of the spectral response already match one or both of these spectra interpolation has no effect; therefore, another type of interpolation could be used to process
srbefore calling this function.
The standards describing mismatch calculations focus on indoor laboratory applications, but are applicable to outdoor performance as well. The 2016 version of ASTM E973 1 is somewhat more difficult to read than the 2010 version 2 because it includes adjustments for the temperature dependency of spectral response, which led to a formulation using quantum efficiency (QE). IEC 60904-7 is clearer and also discusses the use of a broadband reference device. 3
ASTM “E973-16 Standard Test Method for Determination of the Spectral Mismatch Parameter Between a Photovoltaic Device and a Photovoltaic Reference Cell” DOI: 10.1520/E0973-16R20
ASTM “E973-10 Standard Test Method for Determination of the Spectral Mismatch Parameter Between a Photovoltaic Device and a Photovoltaic Reference Cell” DOI: 10.1520/E0973-10
IEC 60904-7 “Computation of the spectral mismatch correction for measurements of photovoltaic devices”